Phil Coulson was defeated, but this allowed Mephisto to demonstrate to his alternate versions how effective they would be if they teamed up to change reality.

(a younger Odin, ancient versions of Black Panther, Iron Fist, Ghost Rider, Phoenix Force, Agamotto (the first Sorcerer Supreme), and Starbrand (a regular human being name V'nn who resembles Red Hulk).

He takes down some of the Multiversal Masters of Evil members and nearly loses his life fighting against an alternate version of Doctor Doom called Doom Supreme (leader of the Multiversal Masters of Evil), but is saved by a Deathlok who tells Robbie that he will be a key player to stopping Mephisto.

After Thor and Odin hit each other with Mjolnir which caused the majority of heroes to be knocked out, Doom Supreme arrives to kill Starbrand and takes Agamotto's eyes.

Doctor Supreme sends out his Multiversal Masters of Evil members King Killmonger (a variant of Killmonger wearing the Destroyer armor), Ghost Goblin (a variant of Green Goblin with Ghost Rider abilities), Black Skull (one of the variants of Red Skull who has the Venom symbiote), a younger version of Thanos called Kid Thanos, Dark Phoenix (an evil version of Phoenix Force) and her pet Berserker (an evil version of Wolverine that was also called Hound).

Robbie Reyes arrives with an alternate version of Tony Stark who operates as Ant-Man on The God Quarry (a boundary between realities) where he realizes he can't activate his powers.

They then shrink down and go to tunnels underneath the battlefield where they find out that Mephisto plans to gain access to universal energy on God Quarry, which will destroy the Multiverse.

Doom Supreme puts a magic barrier to protect himself, but Avengers Prime arrives after dealing with Mephisto, and reveals himself to be Loki.

As a result, other cosmic beings like Galactus, Thanos, Gorr the God Butcher, Celestials and Red Skull converge on Earth.

In the present, Loki manages to dispatch the rest of Doom Supreme and Mephisto's army and creates a portal where the modern and prehistoric Avengers appear.

[19] An ocean beneath the God Quarry threatens to drown multiple Marvel universes, but Old Man Phoenix manages to reseal it briefly.

The two Phoenix Forces and Thor manage to hold back the geyser while Robbie Reyes and Starboard seemingly sacrifice themselves to seal off the flood for good.

Everyone returns back to their respective time and places, with Thor introducing Echo to Freya and Gaea, Nighthawk patrols New York City, Namor is sent to Seagate Prison, the Avengers create statues for Robbie Reyes and Starbrand in the North Pole, Mephisto is tormented by Orb who sits nearby his thrown telling him of things that are happening on Earth, Avenger Prime creates his own Avengers team from across the Multiverse, and Robbie Reyes is revealed to still be alive as he is shown rebuilding his car.

Unfortunately, it’s pretty underwhelming in most of the writing, particularly with Mephisto’s motives and goal, along with how abruptly the villains are defeated so the Avengers could all basically fight a cosmic flood which feels aimless until the solution finally shows up.